The present invention relates to inspection of display substrates. More specifically, the present invention relates to methods and apparatus for reducing the effects of non-uniform cell-gaps in displays.
Active matrix displays, passive liquid crystal displays, plasma displays; and the like are examples of flat panel displays that are commonly used for computers, televisions, monitors, watches, video cameras, PDAs, telephones, and the like. Typically, flat panel displays should appear uniform in contrast and in intensity to a viewer. For example, when all of the pixels on the display are at the maximum intensity, to a viewer, the display should appear uniform.
FIG. 1a illustrates an example of a display having a non-uniform intensity display in response to a uniform image. FIG. 1b illustrates a cross-section of the display in FIG. 1a having a non-uniform cell gap. FIG. 1b includes a first substrate 100, a second substrate 110, and gaps 120 and 130.
Non-uniform gaps (cell-gaps) between first substrate and second substrate typically cause non-uniform pixel intensities on a display. As is illustrated in FIG. 1b, for example, gap 120 is greater than gap 130. As a result, as illustrated in FIG. 1a, the display may be brighter where gap 130 is located, and darker where gap 120 is located, or vice versa.
Displays are typically tested for non-uniformity after they are fully assembled, thus, if non-uniform pixel intensities are detected, that display will most likely be discarded.
What is therefore required are methods and apparatus for reducing the number of discarded displays by compensating for variations in pixel intensity.
The present invention relates to inspection of display substrates. More specifically, the present invention relates to methods and apparatus for compensating for non-uniform output displays.
According to an embodiment a method for operating a display having substrates and a plurality of capacitors formed at predetermined locations between the substrates, includes measuring a capacitance for each of the plurality of capacitors, and determining a cell gap for each of the plurality of capacitors in response to the capacitance for each of the plurality of capacitors. The method may also include determining a cell gap relationship between the substrates in response to the cell gap for each of the plurality of capacitors and in response to the predetermined locations on the display, and determining a first intensity compensating value for a first pixel on an active region of the display in response to the cell gap relationship between the substrates and in response to a location of the first pixel on the display.
According to yet another embodiment, a display includes a pair of substrates having an active region including a plurality of pixels, a plurality of capacitors disposed at predetermined locations between the substrates, and sensors coupled to the plurality of capacitors, configured to measure capacitances of the plurality of capacitors. The display may also include a calculation unit coupled to the sensors, configured to determine a compensating value for at least one pixel of the plurality of pixels in response to the capacitances of the plurality of capacitors and in response to the predetermined locations, and an adjustment unit coupled to receive a location of the at least one pixels, coupled to receive video data for the at least one pixel, and coupled to the calculation unit, the adjustment unit configured to determine a compensated value for the at least one pixel in response to the location of the at least one pixel, the video data for the at least one pixel and to the compensating value for the at least one pixel. A driver unit coupled to the adjustment unit, configured to drive the at least one pixel in response to the compensated value for the at least one pixel is included in one embodiment.
According to yet another embodiment, a method for driving a display including a plurality of pixels includes displaying a predetermined image to the display, capturing an image of the predetermined image on the display with an acquisition unit, and comparing intensities of the predetermined image to the image of the predetermined image to form a difference image. The method may also include determining a cell gap relationship for the plurality of pixels in response to the difference image, and determining intensity compensating values for pixels on the display in response to the cell gap relationship.
Further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and drawings.